The present invention is directed to a method for producing phenol and acetone in which: (1) no side-products are formed due to production of cumene hydroperoxide (CHP); (2) the products are free from dimethyl benzene alcohol (DMBA); (3) the selectivity at cleavage stage approaches the theoretical level of 100%; (4) the stage of product fractionation is greatly simplified due to the production of technical CHP free from acetophenone (AP), DMBA, alpha-methylstyrene (AMS) and products of their conversion; (5) the energy expenses are reduced at least 1.5-2 times; (6) the process construction and technology are substantially simplified; and (7) capital costs for fractionation stage are significantly decreased.
There are numerous patents that refer to various methods for improving the parameters of important commercial process of phenol and acetone production. These patents include, but are not limited to: U.S. Pat. No. 2,663,740; U.S. Pat. No. 4,358,618; U.S. Pat. No. 5,254,751; U.S. Pat. No. 5,530,166; U.S. Pat. No. 5,510,543; and U.S. Pat. No. 5,502,259.
Without exception, the phenol and acetone production processes and methodology taught and disclosed by these patents are generally based on one or more of the following principles:
1. Oxidation of cumene to cumene hydroperoxide to produce the oxidation products containing from 20 to 40% CHP; PA1 2. Concentration of oxidation products by distilling unreacted cumene under vacuum in one, two or sometimes three steps and then directing the recycle to oxidation stage while being pretreated from impurities; PA1 3. Homogeneous cleavage in phenol-acetone-cumene medium using sulfuric acid as a catalyst to produce phenol, acetone, alpha-methylstyrene and by-products (for example, the "phenol tar" which is hard to utilize commercially); PA1 4. Neutralization of sulfuric acid in CHP cleavage products by alkaline agents and removal of salts from the above named products (e.g. Na.sub.2 SO.sub.4, NaHSO.sub.4); PA1 5. Fractionation of cleavage products to produce phenol, acetone, AMS and phenol tar; PA1 6. Hydrogenation of AMS obtained at CHP cleavage stage to convert it into cumene and further recycling cumene to the oxidation stage; PA1 7. Phenol purification from micro impurities with the use of acidic ion-exchange resins; PA1 8. Acetone treatment from impurities with the use of alkalis; and PA1 9. Implementation of a stage of partial thermal cracking of production wastes or their incineration to produce steam. PA1 1. Cleavage of CHP that does not contain DMBA, AP and DCP, elimination of all chemical reactions that form side products; PA1 2. Hydrogenation of DMBA separated from cumene oxidation products to cumene; PA1 3. Production of CHP that is free from DMBA, AP and other impurities conducted by a method of continuous adsorption-desorption; PA1 4. DMBA hydrogenation to cumene; and PA1 5. The use of initial process feed (i.e. cumene) as a desorbent and its further recycle to CHP production stage. PA1 1. Elimination of formation of by-products at the CHP cleavage stage and the fractionation stage; PA1 2. Significant simplification and reduced complexity of equipment necessary for the CHP decomposition stage; PA1 3. Simplification and reduced complexity of CHP cleavage products fractionation (i.e. the number of rectification columns at the fractionation stage can be reduced by a factor of 2 in accordance with the present invention as compared to the conventional scheme); and PA1 4. A significant decrease in energy expenses compared to the conventional scheme (by a factor of approximately 1.5-2).
From the chemical view point, the vast majority of previously known (hereinafter "conventional") processes of phenol and acetone production via the cumene method that exist in the industry and in patent and other literature, can be characterized by the chemical reactions shown in FIG. 1
It is readily apparent to one skilled in the art that the main objective of the designers of this commonly-used process was in finding a way to increase the yield of desired by-product AMS at a CHP cleavage stage (after the ultimate selectivity of 94-95 % theoretical was obtained at cumene oxidation stage).
Two different technologies ("UOP" disclosed in U.S. Pat. No. 4,358,618, and "FAN" disclosed in U.S. Pat. Nos. 5,254,751 and 5,530,166) succeeded in achieving an AMS yield at commercial unit at a level of 80% theoretical. The yield of phenol tar was minimized down to approximately 35 kg/t phenol when cumene usage per 1 ton of phenol was 1307-1310 kg (taking into account the stage of phenol tar cracking) and minimized to 55-58 kg/t and cumene usage of approximately 1330 kg per ton of phenol without phenol tar cracking.
Thus, even the best above-indicated technologies result in losses of initial feed cumene from 33 kg/t to 53 kg/t while the yield of non-utilized wastes remains high. Finally, large number of chemical stages increases the complexity of required implementation technology and further requires increased energy expenditures. Referring now to FIG. 2, a diagram of a typical implementation of conventional technology as described above is shown. This typical implementation is described in whole or in part in the following U.S. patents: U.S. Pat. No. 2,663,740; U.S. Pat. No. 4,358,618; U.S. Pat. No. 5,254,751; U.S. Pat. No. 5,502,259; U.S. Pat. No. 5,510,543; U.S. Pat. No. 5,530,166.
It should be noted that it is nearly impossible to obtain 100% AMS yield utilizing conventional technology due to existing equilibrium of reaction DMBA{character pullout} AMS+H2O and due to formation of AMS dimers and complex phenols form DMBA. With current technology it is also impossible to avoid complexity and high energy requirements of CHP cleavage products fractionation as such products contain AMS, acetophenone and other impurities such as mesityl oxide, hydroxyacetone and others.
Each of the patents mentioned above in connection with FIG. 1 provides some innovation to one or several of the stages of the process of FIG. to improve the parameters and overall results of the process. However, the basic chemistry of the process and its implementation in terms of required equipment remain unchanged.
It would thus be desirable to provide an improved chemical process that reduces the amount of necessary stages for obtaining phenol and acetone via the cumene method. It would also be desirable to provide a new process that results in higher yield of desired products and by-products. It would further be desirable to provide a chemical process that requires less complex equipment implementation than current processes of similar type. It would finally be desirable to provide a chemical process that had significantly lower energy requirements.